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• javax.naming.NameAlreadyBoundException: in glassfish server v2

  - by Nila

  Hi! I'm implementing stateless session bean ejb3 in glassfish server using netbeans. First time, it is working properly. Later, I'm getting the exception as follows: LDR5012: Jndi name conflict found in [SampleEjb3]. Jndi name [Lulu.HellostatelessRemote] for bean [HellostatelessBean] is already in use. LDR5013: Naming exception while creating EJB container: javax.naming.NameAlreadyBoundException: Use rebind to override at com.sun.enterprise.naming.TransientContext.doBindOrRebind(TransientContext.java:292) at com.sun.enterprise.naming.TransientContext.bind(TransientContext.java:232) at com.sun.enterprise.naming.SerialContextProviderImpl.bind(SerialContextProviderImpl.java:111) at com.sun.enterprise.naming.LocalSerialContextProviderImpl.bind(LocalSerialContextProviderImpl.java:90) at com.sun.enterprise.naming.SerialContext.bind(SerialContext.java:461) at com.sun.enterprise.naming.SerialContext.bind(SerialContext.java:476) at javax.naming.InitialContext.bind(InitialContext.java:404) at com.sun.enterprise.naming.NamingManagerImpl.publishObject(NamingManagerImpl.java:237) at com.sun.enterprise.naming.NamingManagerImpl.publishObject(NamingManagerImpl.java:190) at com.sun.ejb.containers.BaseContainer.initializeHome(BaseContainer.java:1015) at com.sun.ejb.containers.StatelessSessionContainer.initializeHome(StatelessSessionContainer.java:232) at com.sun.ejb.containers.ContainerFactoryImpl.createContainer(ContainerFactoryImpl.java:654) at com.sun.enterprise.server.AbstractLoader.loadEjbs(AbstractLoader.java:536) at com.sun.enterprise.server.ApplicationLoader.doLoad(ApplicationLoader.java:188) at com.sun.enterprise.server.TomcatApplicationLoader.doLoad(TomcatApplicationLoader.java:126) at com.sun.enterprise.server.AbstractLoader.load(AbstractLoader.java:244) at com.sun.enterprise.server.AbstractManager.load(AbstractManager.java:225) at com.sun.enterprise.server.ApplicationLifecycle.onStartup(ApplicationLifecycle.java:217) at com.sun.enterprise.server.ApplicationServer.onStartup(ApplicationServer.java:442) at com.sun.enterprise.server.ondemand.OnDemandServer.onStartup(OnDemandServer.java:120) at com.sun.enterprise.server.PEMain.run(PEMain.java:411) at com.sun.enterprise.server.PEMain.main(PEMain.java:338) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.sun.enterprise.server.PELaunch.main(PELaunch.java:412) Then, I'll remove the ejb module from the glassfish server and I'll restart the server. It will work then. So, how to overcome this problem..

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• In Perl, how can a subroutine get a coderef that points to itself?

  - by hillu

  For learning purposes, I am toying around with the idea of building event-driven programs in Perl and noticed that it might be nice if a subroutine that was registered as an event handler could, on failure, just schedule another call to itself for a later time. So far, I have come up with something like this: my $cb; my $try = 3; $cb = sub { my $rc = do_stuff(); if (!$rc && --$try) { schedule_event($cb, 10); # schedule $cb to be called in 10 seconds } else { do_other_stuff; } }; schedule_event($cb, 0); # schedule initial call to $cb to be performed ASAP Is there a way that code inside the sub can access the coderef to that sub so I could do without using an extra variable? I'd like to schedule the initial call like this. schedule_event( sub { ... }, 0); I first thought of using caller(0)[3], but this only gives me a function name, (__ANON__ if there's no name), not a code reference that has a pad attached to it.

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• Executing bat file and returning the prompt

  - by Lieven Cardoen

  I have a problem with cruisecontrol where an ant scripts executes a bat file that doesn't give me the prompt back. As a result, the project in cruisecontrol keeps on bulding forever until I restart cruisecontrol. How can I resolve this? It's a startup.bat from wowza (Streaming Server) that I'm executing: @echo off call setenv.bat if not %WMSENVOK% == "true" goto end set _WINDOWNAME="Wowza Media Server 2" set _EXESERVER= if "%1"=="newwindow" ( set _EXESERVER=start %_WINDOWNAME% shift ) set CLASSPATH="%WMSAPP_HOME%\bin\wms-bootstrap.jar" rem cacls jmxremote.password /P username:R rem cacls jmxremote.access /P username:R rem NOTE: Here you can configure the JVM's built in JMX interface. rem See the "Server Management Console and Monitoring" chapter rem of the "User's Guide" for more information on how to configure the rem remote JMX interface in the [install-dir]/conf/Server.xml file. set JMXOPTIONS=-Dcom.sun.management.jmxremote=true rem set JMXOPTIONS=%JMXOPTIONS% -Djava.rmi.server.hostname=192.168.1.7 rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.port=1099 rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.authenticate=false rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.ssl=false rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.password.file= "%WMSCONFIG_HOME%/conf/jmxremote.password" rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.access.file= "%WMSCONFIG_HOME%/conf/jmxremote.access" rem log interceptor com.wowza.wms.logging.LogNotify - see Javadocs for ILogNotify %_EXESERVER% "%_EXECJAVA%" %JAVA_OPTS% %JMXOPTIONS% -Dcom.wowza.wms.AppHome="%WMSAPP_HOME%" -Dcom.wowza.wms.ConfigURL="%WMSCONFIG_URL%" -Dcom.wowza.wms.ConfigHome="%WMSCONFIG_HOME%" -cp %CLASSPATH% com.wowza.wms.bootstrap.Bootstrap start :end

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• Simple grid layout question

  - by Matt H.

  I can't believe I'm back to this after working with WPF for 3 months :) Consider very common setup: How do I configure the rowheights so that the top and bottom rows (menu bar and status bar) size to fit the height of their content, and the middle row (main content), fills the remaining available space in the program? I can't fix the height of the top/bottom rows because the height of their content can vary. <Window> <Grid> <Grid.RowDefinitions> <RowDefinition/> <RowDefinition/> <RowDefinition/> </Grid.RowDefinitions> <Menu Grid.Row=0> ...menuitems </Menu> <Grid Grid.Row=1> ...main application content here (like most programs) </Grid> <StatusBar> ...statusbaritems </StatusBar> </Grid> </Window>

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• Why do people have to use multiple versions of jQuery in the same page?

  - by reprogrammer

  I have noticed that sometimes people have to use multiple versions of jQuery in the same page (See question 1 and question 2). I assume people have to carry old versions of jQuery because some pieces of their code is based on an older version of jQuery. Obviously, this approach causes inefficiency. The ideal solution is to refactor the old code to use the newer jQuery API. I wonder if there are tools that automate the process of upgrading a piece of code to use a newer version of jQuery. I've never written programs in in either Javascript or jQuery. So, I'd like to hear from programmers experienced in these language about their opinion on this issue. In particular, I'd like to know the following. How much of problem it is to have to load multiple versions of jQuery? Have you ever had to load multiple versions of any other library in the same page? Do you know of any refactoring tools that helps you migrate your code to use the updated API? Do you think such a refactoring tool is useful? Are you willing to use it?

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• Is it practical to program with your feet?

  - by bmm

  Has anyone tried using foot pedals in addition to the traditional keyboard and mouse combo to improve your effectiveness in the editor? Any actual experiences out there? Does it work, or is it just for carpal tunnel relief? I found one blog entry from a programmer who actually tried it: So now I can type using my feet for most of the modifier keys. I am using the pedals as I type this. I am still getting used to them, but the burning in my left wrist has definitely reduced. I think I can also type a little faster, but I am too lazy to do the speed tests with and without the pedals to verify this. On the negative side: Working out where to put your feet when you aren’t typing can be a little awkward. The pedals tend to move around the carpet, despite being metal and quite heavy. Some small spikes might have helped. Although the travel on the pedals is small, they are surprisingly stiff. Another programmer's experience: Anybody with hand pain must get foot pedals, since they can remove a tremendous load from your hands. I have two foot pedals, and use one for the SHIFT key, and the other for the CONTROL key. (I still type META by hand.) I have found that in the process of using the Emacs text editor to compose computer programs, I tend to use the SHIFT, CONTROL and META keys constantly, and it is easy to remove most of this load from one's hands. Some foot switch products: Savant Elite Triple Foot Switch FragPedal Bilbo Step On It!

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• How to limit traffic using multicast over localhost

  - by Shane Holloway

  I'm using multicast UDP over localhost to implement a loose collection of cooperative programs running on a single machine. The following code works well on Mac OSX, Windows and linux. The flaw is that the code will receive UDP packets outside of the localhost network as well. For example, sendSock.sendto(pkt, ('192.168.0.25', 1600)) is received by my test machine when sent from another box on my network. import platform, time, socket, select addr = ("239.255.2.9", 1600) sendSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) sendSock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 24) sendSock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton("127.0.0.1")) recvSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) recvSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, True) if hasattr(socket, 'SO_REUSEPORT'): recvSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, True) recvSock.bind(("0.0.0.0", addr[1])) status = recvSock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(addr[0]) + socket.inet_aton("127.0.0.1")); while 1: pkt = "Hello host: {1} time: {0}".format(time.ctime(), platform.node()) print "SEND to: {0} data: {1}".format(addr, pkt) r = sendSock.sendto(pkt, addr) while select.select([recvSock], [], [], 0)[0]: data, fromAddr = recvSock.recvfrom(1024) print "RECV from: {0} data: {1}".format(fromAddr, data) time.sleep(2) I've attempted to recvSock.bind(("127.0.0.1", addr[1])), but that prevents the socket from receiving any multicast traffic. Is there a proper way to configure recvSock to only accept multicast packets from the 127/24 network, or do I need to test the address of each received packet?

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• RDP through TCP Proxy

  - by johng100

  Hi, First time in Stackoverflow and I'm hoping someone can help me. I'm looking at a proof of concept to pass RDP traffic through a TCP Proxy/tunnel which will pass through firewalls using HTTPS. The problem has to do with deploying images to machines and so it can't be assumed that the .NET framework will be present, so C++ is being used at the deployment end of a connection. The basic system I have at present is a program which listens for client connections on a port then passes any data to a WCF service which stores it as a byte array. A deployment machine (using GSoap and C++) polls the WCF service for messages and if it finds them then passes the data onto the target server process via sockets. I know this sounds horrible, but it works for simple test clients and server passing data to and from simple test client and server programs via this WCF/C++/C# proxy layer. But I have to support traffic from RDP, VNC and possibly others, so I need a transparent proxy to do this and am wondering whether the above approach is worth pursuing. I've read up on SSH tunneling and that seems a possibility. My basic question is is it possible to tunnel RDP traffic over HTTPS using custom code. Thanks John

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• Jboss EAP 5 and Tomcat 6 on the same Win env. (Jboss gets Toncat`s home page when`s up)

  - by Eddie

  Hi guys, I`m newbie to Java technologies, just trying to catch up some idea of it. I was trying to build a java environment to play with Eclipse, Mysql, Tomcat and Jboss and integrate these together. I did: 1. Installed jdk1.6.0_20 (including JAVA_HOME and path variables; I work on Win Vista), mysql 5 and eclipse-jee-galileo (the latest one, 3.6 I believe) and all went good - java programs are compiled and run getting a DB connection. 2. Installed Jboss enterprise-installer-5.0.1.jar with localhost:8080 and this also went good - run.bat started it and I could log in as admin thru its home page. I integrated it with eclipse and could start and stop it from there too. 3. I got apache-tomcat-6.0.26-windows-x86 and this also runs and stops from command line and from eclipse. But this one uses localhost:8080 without asking. Now the problem is when I start jboss I get Tomcat home page and I can`t fix it. Is it probably because both now use localhost:8080? BTW, does Jboss EAP 5 contain Tomcat inside and I shouldn't add that Tomcat separately? Thanks for you help in advance, Eddie

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• What are the most interesting equivalences arising from the Curry-Howard Isomorphism?

  - by Tom

  I came upon the Curry-Howard Isomorphism relatively late in my programming life, and perhaps this contributes to my being utterly fascinated by it. It implies that for every programming concept there exists a precise analogue in formal logic, and vice versa. Here's an "obvious" list of such analogies, off the top of my head: program/definition | proof type/declaration | proposition inhabited type | theorem function | implication function argument | hypothesis/antecedent function result | conclusion/consequent function application | modus ponens recursion | induction identity function | tautology non-terminating function | absurdity tuple | conjunction (and) disjoint union | exclusive disjunction (xor) parametric polymorphism | universal quantification So, to my question: what are some of the more interesting/obscure implications of this isomorphism? I'm no logician so I'm sure I've only scratched the surface with this list. For example, here are some programming notions for which I'm unaware of pithy names in logic: currying | "((a & b) => c) iff (a => (b => c))" scope | "known theory + hypotheses" And here are some logical concepts which I haven't quite pinned down in programming terms: primitive type? | axiom set of valid programs? | theory ? | disjunction (or)

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• How to implement properly plugins in C#?

  - by MartyIX

  I'm trying to add plugins to my game and what I'm trying to implement is this: Plugins will be either mine or 3rd party's so I would like a solution where crashing of the plugin would not mean crashing of the main application. Methods of plugins are called very often (for example because of drawing of game objects). What I've found so far: 1) http://www.codeproject.com/KB/cs/pluginsincsharp.aspx - simple concept that seems like it should work nicely. Since plugins are used in my game for every round I would suffice to add the Restart() method and if a plugin is no longer needed Unload() method + GC should take care of that. 2) http://mef.codeplex.com/Wikipage - Managed Extensibility Framework - my program should work on .NET 3.5 and I don't want to add any other framework separately I want to write my plugin system myself. Therefore this solution is out of question. 3) Microsoft provides: http://msdn.microsoft.com/en-us/library/system.addin.aspx but according to a few articles I've read it is very complex. 4) Different AppDomains for plugins. According to Marc Gravell ( http://stackoverflow.com/questions/665668/usage-of-appdomain-in-c ) different AppDomains allow isolation. Unloading of plugins would be easy. What would the performance load be? I need to call methods of plugins very often (to draw objects for example). Using Application Domains - http://msdn.microsoft.com/en-us/library/yb506139.aspx A few tutorials on java2s.com Could you please comment on my findings? New approaches are also welcomed! Thanks!

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• Why does Clojure hang after hacing performed my calculations?

  - by Thomas

  Hi all, I'm experimenting with filtering through elements in parallel. For each element, I need to perform a distance calculation to see if it is close enough to a target point. Never mind that data structures already exist for doing this, I'm just doing initial experiments for now. Anyway, I wanted to run some very basic experiments where I generate random vectors and filter them. Here's my implementation that does all of this (defn pfilter [pred coll] (map second (filter first (pmap (fn [item] [(pred item) item]) coll)))) (defn random-n-vector [n] (take n (repeatedly rand))) (defn distance [u v] (Math/sqrt (reduce + (map #(Math/pow (- %1 %2) 2) u v)))) (defn -main [& args] (let [[n-str vectors-str threshold-str] args n (Integer/parseInt n-str) vectors (Integer/parseInt vectors-str) threshold (Double/parseDouble threshold-str) random-vector (partial random-n-vector n) u (random-vector)] (time (println n vectors (count (pfilter (fn [v] (< (distance u v) threshold)) (take vectors (repeatedly random-vector)))))))) The code executes and returns what I expect, that is the parameter n (length of vectors), vectors (the number of vectors) and the number of vectors that are closer than a threshold to the target vector. What I don't understand is why the programs hangs for an additional minute before terminating. Here is the output of a run which demonstrates the error $ time lein run 10 100000 1.0 [null] 10 100000 12283 [null] "Elapsed time: 3300.856 msecs" real 1m6.336s user 0m7.204s sys 0m1.495s Any comments on how to filter in parallel in general are also more than welcome, as I haven't yet confirmed that pfilter actually works.

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• Adding a guideline to the editor in Visual Studio

  - by xsl

  Introduction I've always been searching for a way to make Visual Studio draw a line after a certain amount of characters: Below is a guide to enable these so called guidelines for various versions of Visual Studio. Visual Studio 2010 Install Paul Harrington's Editor Guidelines extension. Open the registry at HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\10.0\Text Editor and add a new string called Guides with the value RGB(100,100,100), 80. The first part specifies the color, while the other one (80) is the column the line will be displayed. Or install the Guidelines UI extension, which will add entries to the editor's context menu for adding/removing the entries without needing to edit the registry directly. The current disadvantage of this method is that you can't specify the column directly. Visual Studio 2008 and Other Versions If you are using Visual Studio 2008 open the registry at HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\Text Editor and add a new string called Guides with the value RGB(100,100,100), 80. The first part specifies the color, while the other one (80) is the column the line will be displayed. The vertical line will appear, when you restart Visual Studio. This trick also works for various other version of Visual Studio, as long as you use the correct path: 2003: HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\7.1\Text Editor 2005: HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\8.0\Text Editor 2008: HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\Text Editor 2008 Express: HKEY_CURRENT_USER\Software\Microsoft\VCExpress\9.0\Text Editor This also works in SQL Server 2005 and probably other versions.

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• Optimizing PHP require_once's for low disk i/o?

  - by buggedcom

  Q1) I'm designing a CMS (-who isn't!) but priority is being given to caching. Literally everything is cached. DB rows, DB id queries, Configuration data, processed data, compiled templates. Currently it has two layers of caching. The first is a opcode cache or memory cache such as apc, eaccelerator, xcache or memcached. If an entry is not found in there it is then searched for in the secondary slow cache, ie php includes. Are the opcode caches actually faster than doing a require_once to a php file with a var_export'd array of data in it? My tests are inconclusive as my development box (5.3 of XAMPP) keeps throwing errors installing any of the aforementioned programs. Q2) The CMS has numerous helper classes that are autoloaded on demand instead of loading all files. Mostly each has a require before it so no autoloading needs to take place, however this is not the question. Because a page script can have up to 50/60 helper files included I have a feeling that if the site was under pressure it would buckle because of all the i/o that this incurs. Ignore for the moment that there is output cache in place that would remove the need for what I am about to suggest, and also that opcode caches would render this moot. What I have tried to do is join all the helper files required for the scripts execution in one single file. This is achievable and works well, however it has a side effect of greatly increasing the memory usage dramatically even though technically the same code is being used. What are your thoughts and opinions on this?

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• Can you force a crash if a write occurs to a given memory location with finer than page granularity?

  - by Joseph Garvin

  I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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• JVM terminates when launching eclipse with J2SE 6.0 on mac os x (need J2SE 6.0 for Oracle enterprise

  - by rooban bajwa

  I know my issue has party been addressed at this link http://stackoverflow.com/questions/245803/jvm-terminates-when-launching-eclipse-mat-on-mac-os-with-j2se-60 but it was a year+ ago.. plus the link that's provided in there http://landonf.bikemonkey.org/static/soylatte/ does not seem to be alive (i mean the download section on that link no longer provide the 32-bit port of j2se 6.0 for mac osx 10.5) I am trying to run eclipse 3.5 on mac OSX 10.5. It works fine with J2SE 5.0. But when I installed the Oracle enterprise pack for eclipse - it requires to start eclipse with J2SE 6.0 JVM otherwise it will get disabled. Here's the exact message I get from it - "You are running Eclipse on Java VM version: 1.5.0_22 Oracle Enterprise Pack for Eclipse requires Java version 6 or higher. Click next to configure a compatible Java VM." It asks me to point to J2SE 6.0 JVM, when I do that (i.e point it to "/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home") , it asks to restart eclipse , when I do that, eclipse just bombs .. with JVM terminated error .. SO I need to start eclipse with J2SE 6.0 JVM but eclipse needs carbon which is only available in 32 bits and hence I cann't start eclipse with J2SE 6.0 JVM which is only available in 64bit mode from mac. And the site providing 32 bit port of J2SE 6.0 JVM does not seem to be active anymore.. Can someone help me on this issue, Thanks in advance,

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• Are lambda expressions/delegates in C# "pure", or can they be?

  - by Bob

  I recently asked about functional programs having no side effects, and learned what this means for making parallelized tasks trivial. Specifically, that "pure" functions make this trivial as they have no side effects. I've also recently been looking into LINQ and lambda expressions as I've run across examples many times here on StackOverflow involving enumeration. That got me to wondering if parallelizing an enumeration or loop can be "easier" in C# now. Are lambda expressions "pure" enough to pull off trivial parallelizing? Maybe it depends on what you're doing with the expression, but can they be pure enough? Would something like this be theoretically possible/trivial in C#?: Break the loop into chunks Run a thread to loop through each chunk Run a function that does something with the value from the current loop position of each thread For instance, say I had a bunch of objects in a game loop (as I am developing a game and was thinking about the possibility of multiple threads) and had to do something with each of them every frame, would the above be trivial to pull off? Looking at IEnumerable it seems it only keeps track of the current position, so I'm not sure I could use the normal generic collections to break the enumeration into "chunks". Sorry about this question. I used bullets above instead of pseudo-code because I don't even know enough to write pseudo-code off the top of my head. My .NET knowledge has been purely simple business stuff and I'm new to delegates and threads, etc. I mainly want to know if the above approach is good for pursuing, and if delegates/lambdas don't have to be worried about when it comes to their parallelization.

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• What is the relationship between Turing Machine & Modern Computer ?

  - by smwikipedia

  I heard a lot that modern computers are based on Turing machine. I just cannot build a bridge from a conceptual Turing Machine to a real modern computer. Could someone help me build this bridge? Below is my current understanding. I think the computer is a big general-purpose Turing machine. Each program we write is a small specific-purpose Turing machine. The classical Turing machine do its job based on the input and its current state inside and so do our programs. Let's take a running program (a process) as an example. We know that in the process's address space, there's areas for stack, heap, and code. A classical Turing machine doesn't have the ability to remember many things, so we borrow the concept of stack from the push-down automaton. The heap and stack areas contains the state of our specific-purpose Turing machine (our program). The code area represents the logic of this small Turing machine. And various I/O devices supply input to this Turing machine.

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• jBPM 4.3 Task Notification tag being ignored

  - by user291780

  I have a task with a notification entry but no emails are being generated and no entries in logs. Emails from mail node work fine. What am I doing wrong? Do I have to do anything special to my custom AssignmentHandler impl for notifications? <mail g="216,156,80,40" name="Send email"> <to addresses="[email protected]" /> <subject>Testing the mail activity</subject> <text>This message was sent by the jBPM mail activity tester</text> <transition g="-78,-18" to="User Review" /> </mail> <task g="210,250,92,52" name="User Review"> <description>User Review Task Description</description> <assignment-handler class="com.kevinmoodley.BPMTaskAssignmentHandler"> <description>Review AI Process Failure Assignment Handler</description> </assignment-handler> <notification> <to addresses="[email protected]" /> <subject>Testing from task</subject> <text>This message was sent by the jBPM User Review task</text> </notification> <transition g="-42,-18" name="CANCEL" to="end1" /> <transition g="-42,-18" name="RESTART" to="end2" /> </task> Thanks Kevin

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• VB.NET - Object reference not set to an instance of an object

  - by Daniel

  I need some help with my program. I get this error when I run my VB.NET program with a custom DayView control. ***** Exception Text ******* System.NullReferenceException: Object reference not set to an instance of an object. at SeaCow.Main.DayView1_ResolveAppointments(Object sender, ResolveAppointmentsEventArgs args) in C:\Users\Daniel\My Programs\Visual Basic\SeaCow\SeaCow\SeaCow\Main.vb:line 120 at Calendar.DayView.OnResolveAppointments(ResolveAppointmentsEventArgs args) at Calendar.DayView.OnPaint(PaintEventArgs e) at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer) at System.Windows.Forms.Control.WmPaint(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) According to the error code, the 'for each' loop below is causing the NullReferenceException error. At default, the 'appointments' list is assigned to nothing and I can't find where the ResolveAppointments function is being called at. Private Sub DayView1_ResolveAppointments(ByVal sender As Object, ByVal args As Calendar.ResolveAppointmentsEventArgs) Handles DayView1.ResolveAppointments Dim m_Apps As New List(Of Calendar.Appointment) For Each m_App As Calendar.Appointment In appointments If (m_App.StartDate >= args.StartDate) AndAlso (m_App.StartDate <= args.EndDate) Then m_Apps.Add(m_App) End If Next args.Appointments = m_Apps End Sub Anyone have any suggestions?

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• Basic Tomcat Servlet error.

  - by ajay

  package mypackage; import java.io.*; import javax.servlet.http.*; import javax.servlet.*; public class Hello extends HttpServlet { public void doGet (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { PrintWriter out = res.getWriter(); out.println("Hello, world!"); out.close(); } } web.xml file is as follows: <?xml version="1.0" encoding="ISO-8859-1"?> <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <display-name>Hello, World Application</display-name> <description> This is a simple web application with a source code organization based on the recommendations of the Application Developer's Guide. </description> <servlet> <servlet-name>HelloServlet</servlet-name> <servlet-class>mypackage.Hello</servlet-class> </servlet> <servlet-mapping> <servlet-name>HelloServlet</servlet-name> <url-pattern>/hello</url-pattern> </servlet-mapping> </web-app> I am then doing ant all , ant reload and also /etc/init.d/tomcat restart But I get this error on browser: HTTP Status 404 - /hello/ type Status report message /hello/ description The requested resource (/hello/) is not available. Apache Tomcat/6.0.26 What could be wrong?

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• Eclipse does not refresh project files in package explorer view

  - by EugeneP

  Today I see a strange behaviour of Eclipse 3.5.2 for the first time in 3 months. First, when I run a main function, it runs a previously compiled version. Let's say I press Ctrl+F11 in the window with an open java class and existing main function. Usually it rebuilds the class and runs a new version. Today even if there was a compile mistake, it would run fine. So I guess it does not recompile the class. Next, more strangely, if I intentionally make a mistake in the code and Eclipse underlines those lines in red, still the project Explorer does not mark them as containing errors. They remain of grey color if there were not any errors. First I did not know how to solve this problem. I tried to reopen the project, restart Eclipse and finally reboot the OS. After the tenth attempt, after rebooting, Eclipse said that all project's files are "OUT OF SYNC with the file system". When I pressed "Refresh" - F5 on a project's header name in Project Explorer it finally marked all the files with errors as containing errors and running the main function gave the desired result. An hour of my work passed and this happened again , with the other project. All the same. No marking of files as red, running no matter what old version of class with no compile errors. And since Eclipse does not tell that files are out of sync, simply pressing F5 on a project cannot help. What can you suggest?

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• Are there some cases where Python threads can safely manipulate shared state?

  - by erikg

  Some discussion in another question has encouraged me to to better understand cases where locking is required in multithreaded Python programs. Per this article on threading in Python, I have several solid, testable examples of pitfalls that can occur when multiple threads access shared state. The example race condition provided on this page involves races between threads reading and manipulating a shared variable stored in a dictionary. I think the case for a race here is very obvious, and fortunately is eminently testable. However, I have been unable to evoke a race condition with atomic operations such as list appends or variable increments. This test exhaustively attempts to demonstrate such a race: from threading import Thread, Lock import operator def contains_all_ints(l, n): l.sort() for i in xrange(0, n): if l[i] != i: return False return True def test(ntests): results = [] threads = [] def lockless_append(i): results.append(i) for i in xrange(0, ntests): threads.append(Thread(target=lockless_append, args=(i,))) threads[i].start() for i in xrange(0, ntests): threads[i].join() if len(results) != ntests or not contains_all_ints(results, ntests): return False else: return True for i in range(0,100): if test(100000): print "OK", i else: print "appending to a list without locks *is* unsafe" exit() I have run the test above without failure (100x 100k multithreaded appends). Can anyone get it to fail? Is there another class of object which can be made to misbehave via atomic, incremental, modification by threads? Do these implicitly 'atomic' semantics apply to other operations in Python? Is this directly related to the GIL?

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• Is it possible that a single-threaded program is executed simultaneously on more than one CPU core?

  - by Wolfgang Plaschg

  When I run a single-threaded program that i have written on my quad core Intel i can see in the Windows Task Manager that actually all four cores of my CPU are more or less active. One core is more active than the other three, but there is also activity on those. There's no other program (besided the OS kernel of course) running that would be plausible for that activitiy. And when I close my program all activity an all cores drops down to nearly zero. All is left is a little "noise" on the cores, so I'm pretty sure all the visible activity comes directly or indirectly (like invoking system routines) from my program. Is it possible that the OS or the cores themselves try to balance some code or execution on all four cores, even it's not a multithreaded program? Do you have any links that documents this technique? Some infos to the program: It's a console app written in Qt, the Task Manager states that only one thread is running. Maybe Qt uses threads, but I don't use signals or slots, nor any GUI. Link to Task Manager screenshot: http://img97.imageshack.us/img97/6403/taskmanager.png This question is language agnostic and not tied to Qt/C++, i just want to know if Windows or Intel do to balance also single-threaded code on all cores. If they do, how does this technique work? All I can think of is, that kernel routines like reading from disk etc. is scheduled on all cores, but this won't improve performance significantly since the code still has to run synchronous to the kernel api calls. EDIT Do you know any tools to do a better analysis of single and/or multi-threaded programs than the poor Windows Task Manager?

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• Cannot read values from [NSUserDefaults standardUserDefaults] after synchronize

  - by Nonlinearsound

  In the Application Delegate didFinishLaunching method, I am using the following code to build up a new NSDictionary to be used as the new settings bundle for the user: NSNumber *testValue = (NSNumber*)[[NSUserDefaults standardUserDefaults] objectForKey:@"settingsversion"]; if (testValue == nil) { NSNumber *numNewDB = [NSNumber numberWithBool:NO]; NSNumber *numFirstUse = [NSNumber numberWithBool:YES]; NSDate *dateLastStatic = [NSDate date]; NSDate *dateLastMobile = [NSDate date]; NSNumber *numSettingsversion = [NSNumber numberWithFloat:1.0]; NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys: numNewDB, @"newdb", numFirstUse, @"firstuse", numSettingsversion, @"settingsversion", dateLastStatic, @"laststaticupdate", dateLastMobile, @"lastmobileupdate", nil]; [[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults]; [[NSUserDefaults standardUserDefaults] synchronize]; } Later in another ViewController I am trying to read back a value from that same Dictionary, saved as the NSUserDefaults - well at least I thought it would, but I don't get any valid object pointer for the desired member lastUpdate back there: in .h file: NSDate *lastUpdate; in the .m file in a member function: lastUpdate = (NSDate *)[[NSUserDefaults standardUserDefaults] objectForKey:@"laststaticupdate"]; Even, if I print out the content of [NSUserDefaults standardUserDefaults] I only get this: 2010-04-29 15:13:22.322 myApp[4136:207] Content of UserDefaults: <NSUserDefaults: 0x11d340> This leads me to the conclusion that there is no standardUserDefaults dictionary somewhere in memory or it cannot be determined as such a structure. Edit: Every time, I restart the app ión the device, the check for testValue is Nil and I am building up the dictionary again but after one run it should be persistent on the Phone, right? Am I doing something wrong somewhere in between? I have the feeling that I yet didn't really understand how to load and save settings persistent for a certain application on the iPhone. Is there anything I have to do additionally to this? Integrating a settings.bundle in XCode or saving the dictionary manually to the Documents folder? Can someone help me out here? Thanks a lot!

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